1. Field of the Invention
The present invention relates to a heat exchanger, and more particularly, to a heat exchanger for use in an automobile air conditioning system.
2. Description of the Prior Art
With reference to FIG. 1, a conventional refrigeration circuit for use, for example, in an automotive air-conditioning system is shown. Circuit 1 includes compressor 10, condenser 500, receiver or accumulator 30, expansion device 40, and evaporator 50 serially connected through pipe member 60 which link the outlet of one component with the inlet of a successive component. The outlet of evaporator 50 is linked to the inlet of compressor 10 through pipe member 60 so as to complete the circuit. The length of pipe members 60 to each component of circuit 1 are made such that the circuit is hermetically sealed.
In operation of circuit 1, refrigerant gas is drawn from the outlet of evaporator 50 and flows through the inlet of compressor 10, and is compressed and discharged to condenser 500. The compressed refrigerant gas in condenser 500 radiates heat to an external fluid flowing through the condenser 500, for example, atmospheric air, and condenses to the liquid state. The liquid refrigerant flows to receiver 30 and is accumulated therein. The refrigerant in receiver 30 flows to expansion device 40, for example, a thermostatic expansion valve, where the pressure of the liquid refrigerant is reduced. The reduced pressure liquid refrigerant flows through evaporator 50, and is vaporized by absorbing heat from a fluid flowing through the evaporator, for example, atmospheric air. The gaseous refrigerant then flows from evaporator 50 back to the inlet of compressor 10 for further compression and recirculation through circuit 1.
The condenser 500 which is shown in FIG. 1(a), comprises a heat exchanger 100 formed of a plurality of adjacent, essentially flat tubes 11 having an oval cross-section and open ends which allow refrigerant fluid to flow therethrough. A plurality of corrugated fin units 12 are disposed between adjacent tubes 11. Flat tubes 11 and fin units 12 jointly form the heat exchanger 100. Cylindrical header pipes 530, 540 are disposed perpendicularly to flat tubes 11 and may have, for example, a clad construction.
As shown in FIGS. 3 and 4, each header pipe 530, 540 includes an outer tube 13 which may be made from aluminum and an inner tube 14 made of a metal material which is brazed to the inner surface of outer tube 13. The outer tube 13 is provided with a plurality of first openings 15. The flat tubes 11 are fixedly connected to the header pipes 530, 540 and are disposed in openings 15 such that the open ends of the flat tubes 11 communicate with the hollow interior of header pipes 530, 540. Inner tube 14 includes portions 14a which define openings corresponding to openings 15. Portions 14a are brazed to the inner ends of flat tubes 11 and ensure that tubes 11 are hermetically sealed within header pipes 530, 540 when inserted in openings 15.
Returning again to FIG. 1(a) and 2, header pipe 530 has an open top end and a closed bottom end. The open top end is provided with an L-shaped pipe member 533a of which one end is fixedly and hermetically connected thereto. The other end of L-shaped pipe member 533a is sealed by an inlet union joint 533b which is fixedly and hermetically connected thereto. Inlet union joint 533b is linked to an outlet of the compressor 10 through a pipe member 60. The inlet union joint 533b and the L-shaped pipe member 533a jointly form an inlet union joint assembly 533. Second header pipe 540 has a closed top end and an open bottom end. The open bottom end is provided with an L-shaped pipe member 543a of which one end is fixedly and hermetically connected thereto. The other end of L-shaped pipe member 543a is sealed by an outlet union joint 543b which is fixedly and hermetically connected thereto. Outlet union joint 543b is liked to an inlet of the receiver-dryer 30 through a pipe member 60. The outlet union joint 543b and the L-shaped pipe member 543a jointly form an outlet union joint assembly 543.
Partition plate 200 is fixedly and fluid-tightly disposed within first header pipe 530 at a location about midway along its length and divides header pipe 530 into an upper section 531 and a lower section 532 which is isolated from the upper section 531. Partition plate 300 is fixedly and fluid-tightly disposed within second header pipe 540 at a location approximately one-third of the way along the length of second header pipe 540 and divides the second header pipe 540 into an upper section 541 and a lower section 542 which is isolated from the upper section 541. The location of partition plate 300 is lower than the location of partition plate 200.
With reference to FIGS. 6(a)-6(d) and 7, partition plates 200 and 300 are fixedly and fluid-tightly disposed within header pipes 530 and 540, respectively by the following manner. Since partition plates 200 and 300 are similarly configured, hereinafter, only partition plate 300 is discussed for purposes of illustration. As shown in FIG. 7, partition plate 300 includes a large semicircular portion 301 and a small semicircular portion 302, thereby forming a pair of shoulders 303. The radius of the large semicircular portion 301 is similar to the radius of an outer peripheral surface of header pipe 540, and the radius of small semicircular portion 302 is similar to the radius of an inner peripheral surface of header pipe 540. Semicircular slot 544 is formed at a certain portion of the header pipe 540. The height of the slot 544 is larger than the thickness of the partition plate 300 in order to easily pass the partition plate 300 therethrough. Partition plate 300 is inserted into the hollow interior of header pipe 540 through slot 544 in the direction shown by the arrow "Y" until an arcuate surface of small semicircular portion 302 contacts the inner peripheral surface of header pipe 540. However, the remainder of slot 544 develops an axial air gap 544a. After insertion of partition plate 300 into the hollow interior of header pipe 540, the arcuate periphery of large semicircular portion 301 of partition plate 300 is brazed to the inner peripheral surface of header pipe 540, and the arcuate surface of small semicircular portion 302 of partition plate 300 is brazed to the inner peripheral surface of header pipe 540.
In operation, compressed refrigerant gas from the compressor flows into upper section 531 of first header pipe 530 through inlet union joint assembly 533, and is distributed such that a portion of the gas flows through each of the flat tubes 11 which is disposed above the location of partition plate 200, and into an upper portion of upper section 541. Thereafter, the refrigerant in the upper portion of section 541 flows downwardly into a lower portion of upper section 541, and is distributed such that a portion flows through each of the plurality of flat tubes 11 disposed below the location of partition plate 200 and above the location of partition plate 300, and into an upper portion of lower section 532 of first header pipe 530. The refrigerant in the upper portion of lower section 532 flows downwardly into a lower portion of lower section 532, and is again distributed such that a portion flows through each of the plurality of flat tubes 11 disposed below the location of partition plate 300, and into the lower section 542 of second header pipe 540. As the refrigerant gas sequentially flows through the flat tubes 11, heat from the refrigerant gas is exchanged with the atmospheric air flowing through corrugated fin units 12 in the direction of arrow "W" as shown in FIG. 5. Since the refrigerant gas transfers heat to the outside air, it condenses to the liquid state as it travels through the tubes 11. The condensed liquid refrigerant in the lower section 542 flows through the outlet union joint assembly 543 and into the receiver-dryer 30.
However, in the prior art, only an arcuate periphery of large semicircular portion 301 is placed on a lower end surface 544b of slot 544. Consequently, if the condenser 500 receives an external impact in an assembling process thereof, then the partition plate 300 may be undesirably inclined with an angle which is determined by the size of the axial air gap 544a. With reference to FIGS. 8 and 9, when partition plate 300 is brazed to the inner peripheral surface of header pipe 540 without eliminating the undesirable inclination thereof, cavities 545 and 546 may be created in a substantial brazing portion 14b. The cavity 546 allows the undesirable communication between upper and lower cavities 541 and 542 of the header pipe 540, thereby decreasing the heat exchangeability of the condenser 500. Furthermore, the cavity 545 allows undesirable communication between the lower section 542 of header pipe 540 and the atmosphere, thereby causing leakage of the refrigerant from the condenser 500.